TXS0102: TXS0102DCTR will cause I2C signal quality to deteriorate.

dave lan

Part Number: TXS0102
Other Parts Discussed in Thread: LSF0102

hi sir

The customer used TI's TXS0102, and now it is found in the test that the I2C signal sent by the master will be disturbed, leading to our HDMI test.The customer removed TXS0102, and the I2C signal sent by the master was normal.TXS0102.docx

over 7 years ago

0 Emrys Maier over 7 years ago

TI__Guru* 97046 points

Hi Dave,
I have notified the appropriate applications specialist and he will be back with you soon.

0 ShreyasRao over 7 years ago

TI__Guru 62080 points

Hi Dave,

what is the loading on the IO lines. Are the input signal 50ohm impedance matched?
i have noticed that the rising and falling edge signal integrity is affected by cap loading; greater the cap loading, the greater is the effect.
is the signal quality deterioation leading to communication failure as well?

0 walter liu over 7 years ago in reply to ShreyasRao

Prodigy 40 points

hi ,

the abnormal signal showed below when under HDMI CTS with 750pf CAP on the DDC signal. Abnormal steps indicated by red arrows.

0 ShreyasRao over 7 years ago in reply to walter liu

TI__Guru 62080 points

Walter,

750pF is large enough in my opinion to cause the signal distortion in TXS.
Is there a way to reduce it through board optimization or removal of external cap itself which may be on the line?

0 walter liu over 7 years ago in reply to ShreyasRao

Prodigy 40 points

The 750pf CAP on the DDC signals is the HDMI CTS requirement. any alternative chip to use？

0 dave lan over 7 years ago in reply to ShreyasRao

Intellectual 520 points

Hi ShreyasRao，

The Loading signal is I2C, the matching impedance is 50 Ohm,

Do you mean that the larger the capacitance, the greater the interference?

Looking forward to your reply! thanks~~~

0 ShreyasRao over 7 years ago in reply to walter liu

TI__Guru 62080 points

Walter,

I would suggest trying LSF0102, this is a passive translation device which requires pullup resistors externally for translation.
to get around high capacitance, the pullup can be chosen small enough such that the data rate is maintained.
You can learn more about LSF in these short videos
training.ti.com/logicminute

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TXS0102: TXS0102DCTR will cause I2C signal quality to deteriorate.